Sliding seals used in the handling of abrasive particles such as taconite present a serious wear problem. This problem is particularly severe in connection with magnetic separators because the stray magnetic fields and field gradients promote the accumulation of abrasive particles between the seal surfaces. In one application, U.S. Pat. No. 3,920,543, a filamentary ferromagnetic matrix material such as steel wool or expanded metal in a compartmented matrix device is carried through a processing device such as a feed station with a magnetic head where slurry is fed through the matrix and magnetic particles are retained in the matrix. Following this, the matrix is typically carried through a processing device such as a rinse station where less-magnetic particles are removed from the matrix. The matrix is then moved through a processing device such as a flush station where more-magnetic particles are removed from the matrix. In this operation it is important to prevent the entrapment of air at the feed station, and to minimize the leakage of slurry. Two sets of sliding seals are used: longitudinal seals along the edges of the matrix device and transverse seals between successive compartments. The transverse seals present relatively little problem, because they make intermittent contact with their bearing surfaces and thereby tend to purge accumulated particles. The longitudinal seals, on the other hand, make prolonged contact and may be subject to an internal overpressure which may be substantial at certain locations along their travel. Sealing systems which adequately perform the sealing function typically have a high wear rate, requiring frequent replacement of the flexible lips as well as the surfaces against which they bear. This wear problem adds significantly to the operating cost of these and other separators and may make them economically inapplicable to certain marginal processes.